Quantum dots add value to PV

Research shows that the way scientists look at solar power will be changing constantly in the coming years. Newly developed solar powered cells may soon outperform conventional photovoltaic technology. Scientists from the National Renewable Energy Laboratory (NREL) have demonstrated the first solar cell with external quantum efficiency (EQE) exceeding 100 percent for photons with energies in the solar range. (The EQE is the percentage of photons that get converted into electrons within the device.)

While traditional semiconductors only produce one electron from each photon, nanometer-sized crystalline materials such as quantum dots avoid this restriction and are being developed as promising photovoltaic materials. An increase in the efficiency comes from quantum dots harvesting energy that would otherwise be lost as heat in conventional semiconductors. The amount of heat loss is reduced and the resulting energy is funneled into creating more electrical current.

By harnessing the power of a process called multiple exciton generation (MEG), the researchers were able to show that on average, each blue photon absorbed can generate up to 30 percent more current than conventional technology allows. MEG works by efficiently splitting and using a greater portion of the energy in the higher-energy photons. The researchers demonstrated an EQE value of 114 percent for 3.5 eV photons, proving the feasibility of this concept in a working device.

This could mean solar panels that produce power at much cheaper rates than non-renewable sources! 

Efficiency shows US the way

Americans used less energy in 2011 than in the previous year, due mainly to a shift to higher-efficiency energy technologies in the transportation and residential sectors. Meanwhile, less coal was used but more natural gas was consumed according to the most recent energy flow charts released by Lawrence Livermore National Laboratory.

Wind power saw the biggest jump from .92 quadrillion BTU, or quads, in 2010 up to 1.17 quads in 2011. Hydroelectricity also saw an increase going from 2.51 quads in 2010 up to 3.17 quads in 2011. Hydroelectricity jumped significantly in 2011 because 2011 saw large amounts of precipitation in the Western U.S.

The majority of energy use in 2011 was used for electricity generation (39.2 quads), followed by transportation, industrial, commercial and residential consumption. However, energy use in the residential, commercial and transportation sectors decreased while industrial energy use increased if only slightly.

According to the U.S. Energy Information Administration (EIA), the nation’s solar photovoltaic (PV) capacity now exceeds 3.5 GW. This figure is the result of a new system at the EIA for estimating the lower bound on total installed PV capacity. The figure includes both utility and customer-scale installations. The latter was not captured in previous estimates.

Of this 3.5 GW of installed solar PV, about 30% of it is considered utility-scale solar. The remaining 70% is found in consumer-sited installations, including commercial/industrial (42%) and residential (28%). These data will give researchers the ability to more accurately track small-scale solar grown in the United States. Though, these data will still not capture off-grid PV systems.

New inverter holds promise

An Indiana University-Purdue University Indianapolis assistant professor has invented a new class of power inverter that could put cheaper and more efficient renewable energy products on the market. Professor Afshin Izadian, a researcher at the Richard G. Lugar Center for Renewable Energy at IUPUI, has invented a power inverter that employs just a single switching transistor and generates infinite-level voltages.

Power inverters are at the heart of several renewable energy technologies. Solar power, battery storage, electric vehicles, motor drives and manufacturing robots all use inverters to generate AC power efficiently. However, the current inverters with multiple switching transistors generate limited voltage levels, are heavy, generate unwanted harmonics (voltage frequencies) and require filters to reduce the harmful effects to the electric grid.

Izadian's invention, the result of a creative reconfiguration of an electrical circuit during a laboratory experiment, would make inverters cheaper, lighter and therefore more efficient than current models. While studying how voltage levels and polarities are created in inverters, he made his discovery.

Not only did the bench test work, it led to the discovery of several other circuits and controllers for high-power inverters with lower switching loss, higher voltage performance and lighter reconfigured circuits. For example, unwanted harmonics are greatly reduced with Izadian's invention. This means car manufacturers can reduce the size and insulation of traction motors so that electric vehicles can be made cheaper. The size and weight of the power electronics can also be reduced, which can boost fuel economy in hybrid cars and buses. Such advantages translate into wider adoption of green technologies and more affordable renewable energy for homes, vehicles and businesses.

Who will COP out this time?

Governments must take action and invest in nature to secure the diversity of life on earth and address today’s development challenges – urges IUCN (International Union for Conservation of Nature) at the 11th Conference of the Parties to the Convention on Biological Diversity (CBD COP11), ongoing in Hyderabad, India.

Biodiversity loss continues and has breached safe planetary boundaries. It’s time for a serious check-up on progress we’ve made to turn the Big Plan into Big Action. According to the IUCN Red List of Threatened Species™, out of the 63,837 species assessed, 19,817 are threatened with extinction, including 41% of amphibians, 33% of reef building corals, 25% of mammals, 13% of birds, and 30% of conifers.

It is no more about saving Nature for Nature’s sake but saving it for mankind’s sake!

Biological diversity is essential for our existence. The natural infrastructure of forests, rivers and oceans – with their natural riches and innate ability to help us adapt to climate change and minimise its impacts – offers viable solutions to today’s most pressing development challenges, including social and economic ones.

As IUCN notes, investing in natural infrastructure is a cost-effective way to respond to long-term human needs, including poverty reduction, food security, access to water and energy as well as a stable economy and generation of employment.

The signing of the CBD in 1993 was seen as a great victory for the developing countries. The convention gave the legal sovereignty claims to individual governments to own their biodiversity and to regulate and share its benefits with communities. This was a departure from the earlier approach of biodiversity being ‘common heritage of mankind.’ Unfortunately this novel treaty has remained largely in print. In India, the passing of Biological Diversity Act in 2002 and establishing of National Biodiversity Authority has had least impact in checking biodiversity destruction in the country. Blindly aping the western industrialised model of agricultural and livestock development has meant severe damage to India’s biodiversity.

Meanwhile, the Living Planet Report of 2012 which documents the changing state of biodiversity and its implications, states that due to the consistent trend of over consumption by developed and developing nations, the ecological footprint exceeded the earth’s bio-capacity and the area of land and productive oceans actually available to produce renewable resources and absorb CO2 emissions -- by more than 50 percent! Ecological foot print is larger than bio-capacity. We have been dipping into dwindling reserves for some time now.

Hopefully, some action will emerge out of the Hyderabad meet – in the form of the Strategic Plan for Biodiversity and its 2020 Aichi Targets to save and restore nature.

Baseload: overrated?

Talk renewables and the first doubt voiced is how do we address the intermittency issue? Inevitably one looks for baseload! Who better than Germany to ask! How did Germany switch over directly from nuclear to renewables without first relying on ramped-up coal use during the transition? As a new study shows, renewables completely ‘obliterate’ the need for baseload power. The study’s main question was: How will intermittent wind and solar power affect the grid? And how much electricity will need to be stored?

Dispatchable power generators will mainly have to be flexible, but this requirement can be met in all of the scenarios. And up to a 40% share of renewables, the cost of power storage (or otherwise lost excess power production) remains moderate, only raising the cost of power by 10% in the worst case, Renewables International says.

Renewables International had already found based on its calculations that Germany won’t need to make any real changes to its grid and won’t need very much power storage if it meets the targets that it currently has set for wind and solar. If the targets are met, Germany will get around 40% of its electricity from renewables. As a comparison, it got around 25% of their electricity from renewable sources during the first half of 2012. So far, the effect has mostly been to offset power from natural gas, but it’s been increasingly “cutting into the baseload.” Denmark, which is already sourcing over 40% of its power from renewable sources, hasn’t had to create any major power storage infrastructure so far.

To move beyond 40% to 80% renewable power (the target for around 2050), Germany could need as much as 14 GW of short-term and 18 GW of seasonal power storage to meet its peak power demand of around 80 GW in the moderate scenario. At that point, power prices would be roughly 10% greater than in 2011, but reaching 100% renewable power will be quite expensive indeed. The German engineers estimate that the final 20% will triple the need for power storage, raising prices once again by around 19%. Not only will nuclear disappear but coal power use will fall off, nearly disappearing by the time the country sources 80% of its electricity from renewable sources.

The country’s phaseout of coal power is based not on an official policy, but rather on a general understanding among experts in the power sector that the switch to renewables will gradually obliterate the need for baseload power, says the study. And if Germany can do it, any reason why others can’t?

FITs best

The quota model for renewable energy does not work as well as feed-in tariff models. In a report recently published by Germany’s Agentur für Erneuerbare Energien (Renewable Energy Agency), the feed-in tariff system was shown to deliver a lower cost to consumers than quota systems.

The majority of the EU’s member states use some sort of feed-in tariff system, in which investments are made into renewable energy according to the cost of producing the energy. As time goes on, often the investments are reduced to encourage lower production costs over time.

The rest use a quota system, known in the United States as Renewable Portfolio Standards or Renewable Energy Standards. Here, the prices end users pay for wind energy is consistently and considerably higher than the prices paid in member states with feed-in tariffs. This runs counter to the idea that quota systems are supposed to reward cheap tech and deliver the lowest-cost electricity possible to consumers.

Germany is a model of the feed-in tariff system, having embraced wind energy to the tune of 29,000 MW. A large portion of its wind capacity is located in less than ideal locations — mainly, in mid-Germany. And yet, according to the Renewable Energy Agency, Germans pay €0.089/kWh for wind energy. Compare the United Kingdom, which has much greater wind-producing potential but also a quota system. It would seem easier to produce electricity via wind and therefore lower production costs, leading to lower prices. That would be wrong. Consumers there pay €0.108/kWh.

Feed in tariffs are not without their drawbacks but are still the best bet for encouraging investment in renewables.

What a waste

As a city like Bangalore struggles to tackle its 5000 tonnes of waste generated daily, with residents near landfills up in arms, it seems a logical solution to turn this waste to wealth. In the UK a 60MW energy-from-waste plant in Cheshire backed by Tata Chemicals and E.ON has just been given government approval. Consent was required for the construction of the £250m plant at Lostock, Northwich, after taking into account concerns around its potential health and visual impacts, as well the implications for traffic safety and the local environment. The Lostock plant deals with about 600,000 tonnes of waste-derived fuel a year. This waste has had all the economically recyclable materials removed and would otherwise be sent to landfill for disposal.

There are already umpteen such plants around the world generating power and it would make sense to study the pitfalls and learn well in time. Plans are on in Bangalore to set up a biogas plant among some other waste to energy plans with biomethanation plants taking 3 months to set up. Even these will not be effective if segregation is not done. Supreme Court guidelines say WTE can be an option only if the waste cannot be recycled or composted. Much of the waste, if segregated, can be composted. Segregation will have to start at homes.
So what is a better option – to compost or generate power? Any ideas?